Method of pulp molding



June 5, 19423- c J. CHAPLIN 1321.516#

METHOD OF PULP MOLDNG Filed April 19, 1937 Inventor,

@-7 23 l 30 M 28 @afn/W- Patented June 15, 1943 METHOD oF PULP MoLmNGcharles J. Chaplin, south Portland, Maine, as-

signor to Chaplin Corporation,

Portland,A

Maine, a corporation of Maine Application April 19, 1937, Serial No.137,618

6 Claims.

In certain pulp articles it is desirable and some-y times necessary thatcertain sections or portions be made heavier or stronger than otherportions. Moreover, certain pulp articles must necessarily have, notonly a strong structure, but one which is hard and dense in order thatthe article may most fully serve the purpose for which it is intended.

The production of kcertain articles can fre quently be most economicallyproduced by molding them to the approximately desired shape from aliquid pulp mixture. Such articles after being molded are subsequentlydried and in some cases are nished by being compressed between smoothand heated dies.

With ordinary pulp molding methods, where the pulp fibres are depositedon a foraminous die, by suction, the bres collect rapidly and com-pactlyuntil a certain thickness of deposit is attained over the die. after`which the deposit is relatively slow, or ceases altogether. During thelatter part of this deposit the fibres are not compacted as rmlytogether and any extra-thick molded pulp article or sheet does not havethe density, hardness and strength throughout as is` sometimes necessaryfor particular conditions and results.

In. the manufacture of certain molded pulp arloose and uncompactedformation of bres is frequently desirable. Many of these articles areeither made of absorbent brous materials, where the moisture and greaseof food products must be made heavier, thicker and stronger than otherportions. `Other articles may require that the bre thickness in certainsections be limited in depth or size for some necessary or specic pur-Dose. f

This invention proposes means for producing such an article, anddiscloses one having certain portions of its structure thicker andstronger than other portions with the entire structure so made as to bedense, rm and strong throughout.

Reference is made to the following figures, each or molding die for onepory the dies of Figs. 2 and 3 being consolidated withv ticles such aspie-plates and the like, this rather absorbed by the plate to which theyhave been transferred. or in cases of articles like butter dishes ortable plates designed to hold and retain food products, an extrathickness of fibre deposit in such molded pulp articles, as ordinarilyproduced, increases their ability to retain food products. When thissame thickness or weight of brous deposit is compressed subsequent tomolding, the structure of the interlocking bres on the deposit isaltered and the sheet is made more flexible. l

For the production of hard, dense sheets of reasonable thickness anddepth, it is necessary to employ different methods than'those usuallyemeach other.

Fig. 5 shows the portion formed by the die of Fig."2 consolidated with,and left on the portion formed by die of Fig. 3.

Fig. 6 shows the portion formedl or molded by the die of Fig. 1 beingconsolidated with the'al-A ready assembled vportions formed or molded bythe dies of Figs. 2 and 3.

Fig. 7 shows the consolidated sections being held densely compactedtogether while the moisture remaining therein is being removed by heatfrom the dies.

Fig. 8 shows a somewhat 'enlarged view of the completed article.

It has already been stated, that yiin order to mold or form a dense,compact sheet or structure. there is a deiinite limit to the thicknessof sheet or of structure which can be so formed. This is particularlytrue where fibrous materials have ployed, which ,give a looselycompacted sheet, or

to simply repress a loosely compacted sheet after it has been formed tomake it more smooth, or to give it a finish. Moreover, ordinaryymoulding methods deposit a layer of pulp of generally uniform thicknessover the surface of the die, resulting in the production of a finishedarticle of reasonably uniform thickness, while on certain' articles itmay be necessary that portions be been prepared or processed to increasetheir strength and their' ability to'form and felt into a dense, strongsheet. For these reasons it is necessary, where a molded pulp structureor article is desired having a strong, dense wall, both thicker andstronger than the ordnary molding methods will produce, to providespecial means for securing the desired result. I have accordinglyprovided for the forming or molding of certain portions or parts of thecompleted article on separate foraminous dies and subsequentlyconsolidating these separately formed portions together, under. con- Theordinary milk bottle closure is in the form l of a heavy board discwhich is forced down inside the recess at the top of the bottle, sealingthe milk therein. This closing or sealing disc must be dense, firm andstrong so that it will remain firmly in place in the bottle recess andbe capable of being compressed into this recess with considerable force.

The particular bottle closure just referred to, while serving to retainthe milk in the bottle, allows dirt and other contaminating andinjurious matter to accumulate on this closure disc and in the recess atthe top of the bottle bead over which it is necessary to pour the milkwhen removing it from the bottle.

The article of my invention illustrated more particularly in Fig. 8,provides for a strong lclosure disc like portion and an over-coveringportion lighter in Weight, fitting over and snugly around the topportion of the bead of the milk bottle, protecting the recess and thisbead from becoming contaminated in any Wayand spreading thiscontamination to the milk, itself.

The strong central section which forms the disc portion of the articleof my invention, is compressed into the bottle mouth recess forming atight seal. When it is desired to use the milk or other bottle contents,the entire cap may be readily removed by hand; It also may be re-used asa cover-cap for the bottlebeing easily ref placed by hand as it hasalready been fitted to the bottle mouth recess when originally installedin place. This enables such an article to have a dual use, first, toeffect the original closure of the milk bottle, insuring that thesealing recess and the top of the bottle bead are adequately protectedagainst contamination while the milk is being stored and delivered,andsecond, that this cap can be re-used as may be necessary as aclosure-cap for the bottle, until its contents has been completely used.

In forming the article of my invention, I first form section A on aforaminous die2 (see Fig. l). This die 2 is covered with a moldingscreen 3, and through the die 2, itself, are perforations 4, permittingthe liquid of the pulp mixture from which the article is formed, to bedrawn into chamber 5, by means of suction applied to pipe 6. The chamberon the rear of die 2 is formed by means of a cover plate or othersuitable means indicated at 'I. The molding screen 3 is held on die 2,by means of a retaining ring 8.

For molding or forming section B of my article I provide a forming die 9(see Fig. 2) having perforations I0, therein, said die being coveredwith a forming screen II clamped in place by a clamping member I2. Achamber I2-a is formed between the rear surface of die 9, and

, the clamping member I2, to which 'chamber there is connected pipe I3.When suction is applied to pipe I3 a deposit B of fibrous material isAformed on screen II.

For forming or molding a third portion C of my article, I provide aforming or molding die I4, (see Fig. 3) having perforations I 6,therein,

and covered with a forming lscreen I5 clamped in place by member Il.This member I'I forms a chamber I9, back of die I4, to which chamber isconnected pipe I8. When suction is applied to pipe I8 exhausting the airand water from chamber I9, a pulp fibre deposit C is formed on thescreen I5.

Each of the fibre deposits A, B and C are limited in thickness to adeposit which is firm and dense and well compacted and felted on theforming wire screen on which it is deposited. I do not permit or allowthese deposits to build up to a thickness where the outermost fibres areloosely deposited or improperly felted, due to the loss in suction whichmust necessarily occur on the outer parts of a thick deposit.

For instance, using a certai'n grade or kind of fibres I may find thatthe limit of deposit thickness may be one-eighth of an inch, thisdeposit being made with a suction behind the die of sixteen inchesvacuum, measured by a mercury column. With such a deposit there is, ofcourse, full sixteen inches vacuum or suction at that portion or part ofthe deposit immediately adjacent to the screen, while there is zero orpractically zero suction or vacuum at that portion of the articlefarthest from the screen. Assuming that the increase in vacuum' is univformly progressive, as the screen is approached and dividing the articleinto four parts, in direction of thickness we can assume that thesection next to the screen may be held and compacted under a vacuum offrom twelve tosixteen inches. The next section would be compacted undera vacuum of eight to twelve inches, and the third section, compactedunder a vacuum of from four to eight inches. The last or outermostsection under a vacuum of from zero to four inches.

Practically, the progression of loss of suction or vacuum occurs morerapidly as the distance from the forming wirey increases. Hence, we knowthat with a deposit being formed only one-thirty-second inch thick,instead of oneeighth inch thick, that-there will be available at leastfour times the suction or vacuum for compacting and interfelting thefibres than there `would be available on a one-thirty-second inchthickness located at the outside of a sheet oneeighth inch thick.

It will be readily understood that the vacuum or suction behind amolding die and a screen results in a corresponding pressure beingapplied on the outside rof the molding screen, either to the liquidpassing thru or the fibres being retained by the screen, 0r to thecomplete bre deposit on the screen and alter it has been 17emoved fromthe liquid mixture. The fibrous layer is then subjected to air pressureon the surface of the formed sheet which takes the place of the liquidpressure While the article was being molded. Assume a fair averagesuction on a one-thirty-second of an inch deposit already consideredbeing fourteen inches mercury, this is roughly equivalent to sevenpounds atmospheric pressure. This means that there is available whenforming an article, only one-thirty-second of an inch thick, a pressureof seven pounds to each square inch of articles surface area serving tocompact the bres of this layer together duringformation, rendering themdense and firm.

Attempting to deposit a thicker layer rapidly re-J duces this availablepressure, and can only result in a more loosely and unevenly compactedfibre structure.

For the above reasons, I, therefore, employ a plurality of forming andmolding dies depositing on each die a layer of pulp of only suchthickness as Will cause it to be thoroughly and completely compacted bythe very act of formation. It has already been pointed out that thesubsequent compacting of a thick, loosely formed 1 or molded sheetdisrupts the'bre structure of formation and does not give the requiredresult.'

If no extra reinforced or strengthened section of any particulararticle'is required, yI mould or form complementary sheets, in the formof thin, compact layers and consolidatevthese firmly together to form athick, den'sesheet molded and shaped in the form of the finished articledesired. However, for the particular article illusg trated, it isnecessary that the central portion be reinforced as compared to the rimportions.- To accomplish this I form section C on die |4,'and section Bon die 9.` These dense, compact sections are then consolidated with eachother, as illustrated in Fig. 4, the die 9 then being removed, leavingthe dense layer- B consolidated with the dense layer C already formedand still being retained on die i4.

It win be noted that this laye'r C not @my covers the at, centralportion of my article in-k A and C completely surround and overliedeposit l B, which deposit, in effect, formsa reinforcing andstrengthening member to that portion of the article Where strengthand-stiffness is required.

It has already been pointed out that a method article by means of die23, which heat will turn the Water contained in the article into watervapor or steam, which 'will escape thru the holes i v24 rand 25 into therespective chambers 26 and than kthe central portion, additional meansfor has been provided for producing a molded pulp article made up ofsections densied and compacted by the very molding method employed;These/ sections, however,` contain a certainv amount of water, or otherliquid,.which must be removed beiorea uniform and homogeneous articlestructure is possible. This water removal is most readilyaccomplished'by the application of heat.

For the particular article under consideration, in fact, for any unitaryproduct, it is necessary that the dcnsied compact sections beheldcompacted in themselves and to each other during the time that the watercontainedin them is be ing `removed. To accomplish this I provide twoco--acting and complementary dies 22 and 23, as shown in Fig. '7.

For the removal of the moisture in the form of water vapor or steam Iprovide perforations in each of these dies, in the form of smallopenings 2li in die 22, and 25 in die 23. A chamber 26 is provided indie 22 behindthese openings,

or on the opposite side of the opening, that is in contact with thearticle, and to this chamber is connected pipe 2l. Suction or vacuum maybe applied. if necessary, thru pipe 21 in chamber 26, to assist inremoving the vapor of evaporation.

Die 23 is also provided with a chamber behind the holes 25, this chamberbeing designated at 28, and having a connecting pipe or tube 29. Thisdie 23 is also provided with a heating chamber 30 to which steam orothnenheating vapor or liquid may be supplied through pipe 3|.

/It will be noted that heat is applied to the theY escape and removal isprovided for the water vapor of the central portion, in order that thismay be removed faster than that in the rim portion, so that the completearticle and all sections thereof, will be dried out at approximately thesame time, no portion being overdried and no portion being left wet orsoggy. I

If necessary or desirable, heat may alsobe applied to die 22, by meansof a heating chamber shown by the dotted lines at 32, supplied with `aheating medium thru pipe 33.` In this case, heat conducting ribs orposts 34 may be added tofconnect the outerfwall 35 of die 22 with theinner Wall, which is in contact with the article being dried.v

A further feature incorporated in my method forproducing the kparticulararticle being considered, 'is the control and limitation of thethickness of the edge of the rim portion by the particular dieconstruction and methodl of forma- 'tioniemployedx The particulararticle illustrated 'is -to avoid the possibility of the edge of thecap,

being caught for injured while the bottle is being handled. It isobviousthat if the cap which stands outwardly at the edge for aconsiderable distance, the possibility of this'portion of cap catchingon some kobject duringv handling is increased.' However, I have provideda cap havingl a relatively thin edge, fitting tightly and snugly againstthe bottle lbead, this thin edge offering the minimum of possibility ofinjury during handling.V v

Referring to Fig.' v1 it willbe noted that the pulp deposit on the wirescreen 3 tapers off at 36 due to the limitation of drainage area behindthe wire screen ilk at this point, and where it is held by the clampring 8. Also, referring to Fig. 3 it will be noted that theedge'thickness of ,the article at 31 is very definitely limitated by thediameter of the clamp member Il. This -edge thickness is also nallylimited and controlled by the shape and space allowed between the dies22 and 23 as shownin Fig. 7. I have Y controlled the deposit` thicknessat the extreme edge of my article and held this thin edge in compressedcondition While the water is being removed and the article is beingnished. The nal result is illustrated at 3 in Fig. 8, where it will benoted that the edge thickness-of the article is reduced at point 36somewhatbelow the thickness of the rim at any other point.

While I have discussed the method of my invcntion as particularlyapplied to the manufacture of milk bottle caps, it is obvious that thismethod may be utilized to great advantage in the manufacture of anyarticle where a dense, compact and rigid structure is necessary. It isparticularly applicable in the economical production of certain articlesby the simple molding processes herein disclosed, such articles havingheretofore been necessarily produced by the cutting of previously madesheets, and the assembling of these sheets together While dry by meansof adhesives, pressing, rolling or Winding'these cut sheets in place toproduce the article. These methods-are not only expensive in productiondue to the fact that the original sheets have to be made, dried, andthen cut and made over into the article, with the addition of adhesivematerials but further there is excessive Waste of sheeted material incutting and forming of shaped articles.

As examples of other articles which may be economically produced by the`methods herein disclosed are tubes, cones, cups and similar objectswhere strength and rigidity are necessary at low cost.

It will Ithus be seen, that I have provided a new method of producinguseful articles. This method includes primary molding or forming ofsections of the article, each having special characteristics, theconsolidating of these sections together to form an article thedifferent parts or areas of which are especially adapted 'for theparticular use to which they will be put, and'of removing the Waterremaining in or betweenthe l.several sections while retaining them inrm',

compacted condition and producing a uniform structure. I also'providemeans for removal of water or water vapor more rapidly in some thickportions of an article of non-uniform thickness than in other thinportions, eiecting' uniform drying of the completed article in densifiedor compact condition.

The article produced by my method has new and novel characteristics, andwhat I claim for both article and its method of production is:

1. The method of producing a molded, fibrous pulp article whichcomprises molding a dense relatively thin and highly compacted contouredsection of pulp on a contoured,'pulp forming die, similarly andseparately forming a second pulp section of lesser area than said rstsection, similarly and separately forming a third section of pulp of an-area substantially co-extensive with said first mentioned section,assembling these contoured sections of pulp in compacted conditionindividually and with each other, positioning said first and thirdmentioned sections to form the-outer surfaces-of the finished article,and removing fluids contained therein.

2. The method ofproducing a fibrous article which comprises forming on adie, a dense, relatively thin, highly compacted, contoured sheet' havingconnected wall portions extending at an angle to each other, forming asecond thin and compacted sheet contoured to `overlie and t a portiononly, including the 4angularly disposed until the'water or other liquidcontained thereinA has been removed.

3. The method oi producing va fibrous pulp article which comprisesmolding on a foraminous die, to its approximate nal shape, a contoured.thin, relativelydense, compact sheet, forming on a second contoured diea thin, compact sheet of lesser area, and contoured to overlie and t aportion only of the dense sheet formed on the rst mentioned die,compacting the sheets with each other, and holding saidsheets in compactcondition until the water or other liquid contained therein has beenremoved.

4. The method of producing a fibrous pulp article which comprisesmolding on a foraminous die, to its approximate final shape, acontoured, dense, compact sheet, forming on a second contoured die vacompact sheet of lesser area andl contoured to overlie and t a portiononly of the surface of the article formed on the first men` tioned'die,molding on a third foraminous die a.dense, compact sheet of an areasubstantially coextensive with that of the article formed on the firstmentioned die, assembling the sheet formed on the`second mentioned diewith the sheet formed on the rst mentioned die, assembling the sheetformed on the third mentioned die in overlying relation with the sheetformed on the second mentioned die and already assembled to overlie aportion only of the sheet on the first mentioned die, said sheet formedon the third mentioned die overlying both of the other sheets, andholding all three sheets in compacted condition in themselves and witheach other, until the water or other liquid contained therein has beenremoved.

5. The method of producing a fibrous pulp article which comprisesmolding on a foraminous die to its approximate nal shape, a contoured,

thin relatively dense, compact sheet of pulp..

formingon a second contoured die a thin compact sheet of lesser area,and'contoured to overlie and iit within a portion only of the rstmentioned dense sheet, compacting the sheets With each other` underpressure, removing fluids contained therein by the application of heatand suction, and vholding said sheets in compact condition until saidfluids have been removed.

6. The method of producing a brous pulp article which comprises moldingon a foraminousl die, to its approximate final shape, a contoured,dense, compact sheet of pulp, forming on a second contoured die, acompact sheet oi lesser area, contoured to overlie and t a portion onlyof the surface of the article formed on the rst mentioned die, moldingon a third foraminous die a dense compact sheet, assembling the sheetformed on the second mentioned die with the sheet formed on the firstmentioned die, assemblingthe sheet formed on the third mentioned die inoverlying relation to the sheet formed on the second mentioned die, andalready assembled to overlie a portion only of the sheet on the firstmentioned die, said sheet formed on the third mentioned die overlyingboth of the other sheets, applying pressure to said assemblage tocompact the sheets together, removing uids contained in the assemblageby the application of heat and suction, and maintaining all threelsheets in compacted condition in themselves and with each other untilsuch fluids have been

